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Lock 21 Peterborough Lift Lock

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Peterborough Lift Lock 21
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mile 89

From Ashburnham lock 20 to the Peterborough Lift Lock is a distance of 1.1 miles. The canal is surrounded by a park on both sides with picnic tables and manicured lawns. Unfortunately the sides of the canal tend to shoal near the edges and most cruising boats will want to leave at least 15 feet between them and the shoreline.

below the Lift Lock a park runs along the canal

Upstream from the railroad bridge your passage may well be blocked by a swing road bridge as lock staff from 20 have to grab a bike and peddle the several hundred yards to the bridge to open it.

As you approach the lift lock itself the Friends of The Trent Severn Visitor Center is on the west side downstream of the locks itself. There is a day use tie-up wall in front for those wishing to visit the center. They maintain an interesting selection of photographs and other reading materials which chronicle the historic construction project as well as a extensive selection of books of regional content. If you have not yet got you charts of the waterway you can pick them up here.

To the east side, across the road is the Lift lock Golf land golf course where there is a small chip truck style outlet in case the kids get impatient waiting for the lock.

The lock itself is perhaps the best known landmark on the entire waterway and a ease to use for the transient boater. You will be tied up on either side by looping your lines around a horizontal bar. There is no fighting of lines or surge to worry about so you can enjoy the show as you ascend.

There is no overnight mooring between 20 and below the lift lock 21, however you can tie-up above the lock see next page. The reason for this is that the water level here changes during the non operating hours

Lock 21 Peterborough Lift Lock

ID Mile Kilometers lift length Sill Depth Preferred side
# 21 90.1 145.06 65' 140' 7' Starboard

Hydraulic lift locks

Peterbourgh Lift Lock

The next engineering feat you will encounter on the waterway are the lift locks the first being Lock 21 in Peterbourgh at mile 90.1. The Peterbough lock is by far the most developed and scenic as well as home to the Trent Severn Visitors centre. In fact these locks are simple and elegant. The construction of the locks is a story unto itself we will drift too far here.

The next example of the hydraulic lift locks will not be encountered until mile 169.4 and the Kirkfield hydraulic lift lock 36. The difference between these two locks is night and day. Kirkfield is close to the middle of nowhere, even if a pretty countrified nowhere, it marks the highest point on the Trent Severn Waterway. By the time you reach here from whichever end you begin you will have settled into the routine and should enjoy the stay.. There are restaurants close by and plenty of tie up spaces.

The unique lift locks operate by using hydraulic pressure. Within a closed system any displacement of volume in one container will transfer the equal amount to the other container. In the case of the Trent Severn Lift Locks those containers are the huge 140 foot long, steel tubs containing 330,000 gallons of water weighing 1,500 tonnes .

hydrostatic pressure example Hydrostatic displacement Kirkfield lock tub

Beneath the lock tubs are located monster hydraulic rams which raise and lower the locks. Each ram is 65 feet long by 7.5 foot diameter extending some 75 feet below the lock to their footings on top of ten ton granite block, resting on bedrock. Both tubes are connected by high pressure pipe and other control pumps and fittings. In practice, the procedure used to raise boats is to fill the upper tub with an extra foot of water, and then vent this water volume into the lower locks chamber, the difference in weight then raises the lower lock.

There are provisions for mechanically pumping water to adjust discrepancies and the staff test run the system before ever letting a boat in so first lift in the morning is before the opening hour.

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